Both leafhopper population numbers and X-disease phytoplasma concentration in the tree are likely to be higher after harvest. When phytoplasma concentration in the tree is higher, leafhoppers are more likely to acquire and transfer the pathogen. It is critical to monitor and manage leafhopper vectors during this high-risk period.
Use yellow sticky cards or sweep nets to monitor your leafhopper population. Place traps on orchard borders, in areas of concern in your block and throughout block. Approx. 1 trap per two acres. Monitor weekly. Use presence (an average of 1 leafhopper per trap) as a threshold to spray. Identify leafhoppers that vector X-disease phytoplasma. For a gallery of vector images see http://treefruit.wsu.edu/vector-gallery/
Rotate leafhopper products when populations are present. Manage leafhoppers when they are present – generally after harvest through October based on monitoring. If leafhoppers are present spray rotating between pesticide groups. With the residual of common (conventional) products sticky cards will likely show 21-30 days of control necessitating 4 to 6 after harvest sprays per season. Remember it takes several weeks after feeding on an infected plant for a leafhopper to be able to transmit the phytoplasma. The phytoplasma has to pass through the insect gut, into the ‘blood’, and to the salivary glands before it can be excreted into a new plant with the saliva. Every two to three weeks sprays should be the shortest interval needed. More frequent sprays will mean you likely run out of legal applications before the end of the season when transmission is likely to be highest. See product efficacy tables here http://treefruit.wsu.edu/crop-protection/disease-management/western-x/
Corina Serban, WSU Extension (509) 574-1595 firstname.lastname@example.org
Tianna DuPont, WSU Extension (509) 293-8758 email@example.com
Bernardita Sallato, WSU Extension (509) 439-8542 firstname.lastname@example.org
Fruit Matters articles may only be republished with prior author permission © Washington State University. Reprint articles with permission must include: Originally published by Washington State Tree Fruit Extension Fruit Matters at treefruit.wsu.edu and a link to the original article.